Proportional force amplifier

ABSTRACT

A system for converting a low-force mechanical input to a relatively high force mechanical displacement in a working element on a one-to-one ratio relative to the displacement of the input through the application of a hydraulic power boost.

United StateSPatent 1191 Clark 5 1 Apr. 2, 1974 I 1 PROPORTION/1L FORCE AMPLIFIER 2,574,335 11/1951 Leduc 91/378 [75] l-nvcnton Ray Clark, Pcwau'kcc wis- 3,(199,94() 8/1963 Lcduc 91/378 [73] Assignee: Applied Power Industries, Inc., FOREIGN PATENTS OR APPLICATIONS Milwaukee, wi 868,247 9/1941 France 91/378 1,117,008 1/1955 France 91/49 [22] Filed: Dec. 3, 1971 [2]] App], No,; 204,539 Primary Examiner'Edgar W. Geoghegan Assistant ExaminerA. M. Zupcic Att ,A 1, F JhJ.B ;Ed'dE. 52 11.5. c1 91/49, 91/376, 91/417 D gen yme 511 1111. C1. Fl5b 13/02,1=151 9/0s,1=15b 15/17 [58] Field of Search 91/47, 49, 378, 417, 374, I

. 91/376, 428 [57] ABSTRACT.

' A system for converting a low-force mechanical input [56] References cued to a relatively high force mechanical displacement in a UNITED STATES PATENTS working element on a one-to-one ratio relative to the 3,019,770 2/1962 Balass' 91/376 displacement of the input through the application of a 1,548,232 8/1925 Westbrook... 91/376 h d lic o r boost 1,954,379 4/1934 Eller 91/378 2,813,519 11/1957 Persson e1 a1 91/378 6 Claims, 1 Drawing Figure PATENTEI] APR 2 I974 mm Fm mw mm mv mm mm mw Y H, mm E mm, mm m J 7 /A H I l H I v v PUJ 0 NJ mm Wm am mmfi MUM 0 Z H i y L M g V k T v a H mm wwm 5 W aw mm \L vm Gm mm NN\ A WW Q i v QW 9 Q E vv 1 a PROPORTIONAL FQRCE AMPLIFIER This invention relates to a hydraulic force amplifier or power assist system wherein a manual, mechanical input displacement will cause a displacement in a working element in the same direction in a one-to-one proportion to the input but at a greatly increased force. For example, the system of this invention provides means of converting a movement at a force from about 1 to lbs. to a similar movement with a force of 100 to 1,000 lbs.

An objective of this invention is to provide a hydraulic force amplifier that provides a power assist to a manual input to move the working element approximately the same distance as the input.

Another important objective of this invention is to provide a hydraulic force amplifier or power assist means wherein, if a back pressure is transmitted through the working element it is resisted by the amplifier assembly and is not transmitted to the manual control.

A still'further objective of this invention is to provide a power amplifier wherein means are provided to permit manual override in the event .of a loss of hydraulic power. 1

A further objective of this invention is to provide a hydraulic force amplifier or power assist wherein accurate movement of a working element is accomplished without the necessity .of a feedback linkage .to a controlling element. A still further objective of this inventionis to provide a power amplifier of simple design and rugged construction that is suitable for applications in industrial and material handling environments.

More particularly, the amplifier or power assist system of this invention comprises a housing having a cylindrical bore therein for slidably receiving a piston which divides said bore into a first or. control chamber, and a second or pressure chamber in constant communication with a fluid pressure source. The piston has first and second faces on opposite sides exposed to said first and second chambers respectively, with the first face being approximately half the size in area of said second face. piston rod extends from the piston through one end of the housing and has means on the outer end thereof for attaching a work load. A sleeve is received on a reduced diameter portion of the rod exterior of the housing, and is axially slidable thereon between front and rear stop means formed by side walls defining the reduced diameter portion. The sleeve has axially spaced inwardly directed wall portions in sliding'engagement with the rod and defines an annular chamber therebetween around the periphery of the rod. A passageway means is located within said rod and includes a first conduit opening at one end into an orifice in the peripheral surface of said rod, andcommunicaring at its other end with a reservoir at atmospheric pressure. A second conduit communicates the annular chamber with the second or control chamber. A third conduit communicates the secondor pressure chamber to a second orifice in the peripheral surface of the rod. This second orifice is axially spaced from the firstmentioned orifice, by the axial distance between said inwardly directed wall portions. The inwardly directed wall portions normally block the orifices when the amplifier is in the'null and balanced position. The sleeve is operably connected to the manual input meansand is slidable in response thereto. Since the wall portions of the sleeve are spaced exactly the same distance as the orifices, the slightest movement of the sleeve will uncover one of the orifices and communicate the control chamber to either the pressure source or the reservoir, depending upon the direction of movement of the sleeve, to create a pressure differential between the first and second chambers thereby causing the piston and rod to shift. The piston and rod will move relative to the sleeve until the orifices are again covered. The degree of displacement of the piston and rod will equal that of the sleeve. 7

These and other objects of the invention will become more apparent to those skilled in the art by reference to the following detailed description when viewed in light of the accompanying drawing wherein:

The single FIGURE is a cross-sectional view of the proportional force amplifier-power assist system of this invention including a schematic illustration of the manual input means.

Referring now to the drawing wherein like numerals indicate like parts, the numeral 10 generally indicates the force amplifier-power assist system of this invention. The principal components of this system include a manual control mechanism 12 and a housing 14 comprising a cylindrical side wall member 16 defining a longitudinal cylindrical bore 18. The cylindrical member 16 is closed at oneend by means of a porting block 20 and at the other end by an end plug22 having an axial opening 24 communicating the cylindrical bore 18 to the. exterior of the housing. Slidably received in the bore 18 is an actuator piston 26 having a piston rod 28 attached thereto which extends through the opening 24 and beyond the housing 14. Any suitable load handling adapter may be attachedto the end 30 depending upon type and direction of movement to be transmitted to the load. Likewise, the porting block 20 includes means for attaching the housing to a suitable support. The piston 26 and the closure plug 22 include conventional annular sealing rings 32, 34 and 36 to prevent fluid leakage.

The piston divides the bore 18 intoa first chamber 38, hereinafter referred to as the pressure chamber, and a second chamber 40, hereinafter referred to as the control chamber. The pressure: chamber 38 is under static system pressure by means of pressurized hydraulic fluid introduced through port 42 and connector 44. The piston 26 has a first face 46 exposed to the pressure chamber 38 and a second face 48 exposed to the control chamber 40, with the working surface area of the first face 46 being approximately half that of face 48. The piston and rod are caused to move by differential pressures created by varying the pressure in chamber 40 in a manner to be explained in detail below.

A control member in the form of a concentric sleeve 68 is slidably received on the reduced diameter portion 54 of the piston rod 28. The sleeve includes axially spaced inwardly directed wall portions and 72 having surfaces which slidably engage the surface of the reduced diameter portion of the rod, and which define an annular chamber 74 therebetween. The reduced diameter portion 54 is defined by end walls 55 and 57 which function as front and rear stops respectively for limiting the sliding motion of the sleeve 68. An attachment projection 59 is provided on the sleeve 68 to which a cable 61 is attached. The cable leads to the lever-operated manual control means, whereby movement is imparted to the cable 61 and consequently to the sleeve 68 by moving the handle 63 in the direction of the arrow.

Passageway means is provided in the piston rod 28 and includes a first conduit 50 extending centrally and axially of the piston rod 28 opening at one end to an orifice 52 on the peripheral surface of a reduced portion 54 of the piston rod 28 via transverse passageway 56. The conduit 50 is communicated at its other end to a passageway 58 in elongated nipple 60 extending from the supporting block 20 inwardly of the bore 18. The nipple is slidably and telescopically received in the conduit 50 and a sealing ring 62 is provided to prevent leakage between the outer surface of the nipple and the inner surface of the conduit 50 as the piston moves relative to the nipple. The conduit 58 is communicated to a reservoir at tank pressure via port 64. A second conduit 76 communicates the control chamber 40 to the annular chamber 74 through orifice 80. A third conduit 82 communicates pressure chamber 38 to orifice 84 via transverse passageway 86.

The operation of the proportional force amplifierpower assist system of this invention is as follows: the handle 63 is moved clockwise or counterclockwise as indicated by the arrows which produces a corresponding longitudinal movement in the push-pull cable 61. This moves the sleeve 68 either to the right or the left, depending upon the direction of the movement of the handle 63. In the position shown, the sleeve blocks each of the orifices 52 and 84, and the piston and rod are in the null or balanced position. To move the piston and piston rod 28 to the right, the lever'63 is shifted to the right a calibrated distance causing the sleeve 68 to move to the right thereby exposing the orifice 84, and thereby fluid under pressure from chamber 38, to the annular chamber 74. The pressure is transmitted to control chamber 40 via second conduit 76 wherein a differential pressure is created causing the piston to move to the right. The piston and piston rod move relative to the Sleeve 68 Until the orifice 84 is again covered by wall portion 72 thereby cutting off the flow of fluid under pressure to the control chamber 40. At this time, the amplifier again will be in the null and balanced position. It is to be understood that a movement in the control memberor sleeve 68 causes a movement in the piston and rod a corresponding distance or, in other words, in a l 1 ratio. This in turn moves a load attached to the end of the piston rod 28 the desired amount and direction utilizing the power assist of the amplifier.

By using the amplifier of this invention in the manner described, it is possible to amplify the force applied to the cable 61 by to 100 times. For example, ten pounds of input force by means of cable 61 will result in 1,000 pounds of output force by means of the rod 28.

for example, but since the piston 26 moves relative to the sleeve, which will remain stationary, the reservoir or tank orifice 52 will be uncovered thereby communicating the control chamber 40 to tank pressure. The resulting pressure differential between chambers 40 and 38 will cause the piston 26 and rod 28 to move back to the left until both of the orifices 52 and 84 are again covered by the inwardly directed portions of the sleeve 68. This will be the original position of the piston and rod prior to the application of the sudden load.

The distance between the orifices 52 and 84 is equal to the distance between the inwardly directed wall portions and 72. Such spacing virtually eliminates any lost motion between the piston and sleeve upon opening of the orifices. Also, the diameters of the orifices of the passageways 52 and 84 are relatively small compared to the stroke of the piston 26; for example, in the order of 30/1000 in. compared to 2 in.. Therefore, due to the small size of the orifices, and the spacing of the orifices and the edges of the inwardly directed wall portions, the piston need move only a relatively small distance relative to the sleeve or vice versa before full pressure or full exhaust is communicated to the control chamber 40. The increase in the pressure in chamber 40, therefore, is relatively great compared to the dis: tance of movement of the piston 26 and connected rod 28.

In the event that there is a loss of pressure, the rod can be manually shifted without power assist in either direction by actuating the handle 63 to cause the sleeve to abut against either the forward stop 55 or the rearward stop 57, depending upon which direction the rod is to be moved.

The sleeve 68 is provided with sealing rings 88 and 90 to prevent leakage between the rod and sleeve. It is to be noted that an annular groove 92 is provided in the periphery of the rod 28 between the fluid pressure orifice 84 and the sealing ring 90. The groove 92 is communicated to fluid under reservoir pressure from conduit 50 and serves as a buffer between the highly pressurized fluid at orifice 84 and the sealing ring 92. In this manner. the sealing ring will not be subjected to high pressure thereby reducing seal friction and eliminating seal extrusion or the like.

In a general manner, while there has been disclosed an effective and efficient embodiment of the invention, it should be well understood that the invention is not limited to such embodiment, as there might be changes made in the arrangement, disposition, and form of the parts without departing from the principle of the present invention.

I claim:

1. In a force amplification system, a manual input means, a housing having a cylindrical bore therein, a piston slidably received in said bore dividing said bore into first and second chambers, first and second faces on opposite sides of said piston exposed to said first and second chambers respectively, said first face being approximately half the size in area of said second face, a piston rod attached to said piston and extending exteriorly of said housing through an opening therein, a pressure source, an inlet port constantly communicating said first chamber to said pressure source, a reservoir, control means movably mounted on the exterior of said piston rod outside of said housing and operably connected to said manual input means for movement in response thereto, passageway means in said piston rod communicating said pressure source, second chamber and said reservoir to said control means, said control .5 means extending across said'passageway means and having first and second positions wherein said second chamber is communicated to said reservoir and said pressure source, respectively, to cause movement of said piston in response to said manual input means in the same direction and a distance equal to the movement of said control means, and said control means having a third position wherein said second chamber is blocked from communication with said reservoir and pressure source to maintain said piston in a selected position.

2. The system of claim 1 wherein said manual input means comprises a push-pull cable assembly.

3. The system of claim 1 wherein said control means is a sleeve concentrically mounted on said piston rod, and said sleeve comprises, first and second inwardly directed wall portions slidably engaging said rod, said wall portions being axially spaced and defining an annular chamber therebetween with said rod, and said passageway means comprises a first orifice on the exterior of said rod, a first conduit communicating said first orifice with said reservoir, a second orifice on the exterior of said rod and axially spaced from said first orifice, a second conduit communicating said second orifice with said pressure source, a third orifice on the exterior surface of said rod approximately midway between said first and second orifices and opening into said annular chamber, and a third conduit communicating said third orifice and said annular chamber with said second chamber, said first and second wall portions covering said first and second orifices when said control means is in said third position.

4. The system of claim 3 wherein the shortest distance between said first and second wall portions is equal to the shortest distance between said first and second orifices.

5. The system'of claim 4 wherein said rod has an axially extending portion thereon of reduced diameter, said sleeve being slidably mounted on said rod along said reduced portion, and including first and second axially spaced stop means at each end of said reduced portion for limiting movement of said sleeve.

6. The system of claim 3 wherein when said control means is in said first position, said first orifice is uncovered and communicates with said third orifice, and when in said second position, said second orifice is uncovered and communicates with said third orifice. 

1. In a force amplification system, a manual input means, a housing having a cylindrical bore therein, a piston slidably received in said bore dividing said bore into first and second chambers, first and second faces on opposite sides of said piston exposed to said first and second chambers respectively, said first face being approximately half the size in area of said second face, a piston rod attached to said piston and extending exteriorly of said housing through an opening therein, a pressure source, an inlet port constantly communicating said first chamber to said pressure source, a reservoir, control means movably mounted on the exterior of said piston rod outside of said housing and operably connected to said manual input means for movement in response thereto, passageway means in said piston rod communicating said pressure source, second chamber and said reservoir to said control means, said control means extending across said passageway means and having first and second positions wherein said second chamber is communicated to said reservoir and said pressure source, respectively, to cause movement of said piston in response to said manual input means in the same direction and a distance equal to the movement of said control means, and said control means having a third position wherein said second chamber is blocked from communication with said reservoir and pressure source to maintain said piston in a selected position.
 2. The system of claim 1 wherein said manual input means comprises a push-pull cable assembly.
 3. The system of claim 1 wherein said control means is a sleeve concentrically mounted on said piston rod, and said sleeve comprises, first and second inwardly directed wall portions slidably engaging said rod, said wall portions being axially spaced and defining an annular chamber therebetween with said rod, and said passageway means comprises a first orifice on the exterior of said rod, a first conduit communicating said first orifice with said reservoir, a second orifice on the exterior of said rod and axially spaced from said first orifice, a second conduit communicating said second orifice with said pressure source, a third orifice on the exTerior surface of said rod approximately midway between said first and second orifices and opening into said annular chamber, and a third conduit communicating said third orifice and said annular chamber with said second chamber, said first and second wall portions covering said first and second orifices when said control means is in said third position.
 4. The system of claim 3 wherein the shortest distance between said first and second wall portions is equal to the shortest distance between said first and second orifices.
 5. The system of claim 4 wherein said rod has an axially extending portion thereon of reduced diameter, said sleeve being slidably mounted on said rod along said reduced portion, and including first and second axially spaced stop means at each end of said reduced portion for limiting movement of said sleeve.
 6. The system of claim 3 wherein when said control means is in said first position, said first orifice is uncovered and communicates with said third orifice, and when in said second position, said second orifice is uncovered and communicates with said third orifice. 